Suspension thermal spraying (STS) techniques enable the use of sub-micron powder particles as feedstock, as opposed to the traditional use of dry powders with micrometric size, leading to nano-structured coatings. Yttria-stabilised zirconia (YSZ) is a widely used thermal barrier coating in aeroengines and suspension sprayed YSZ has been reported to present lower thermal conductivity, enhanced phase stability and strain tolerance. The effect of processing parameters on the microstructure, especially porosity, is largely overlooked in the literature despite its central effect on performance. The objective of this proposal is to understand the evolution of porosity on YSZ coatings deposited via STS on as-received conditions and after heat treatment at 1100, 1200, 1300 and 1400°C, studying the sintering of nanopores into micro-features due to the capability of SESANS to measure up to 20 um.